Elevator Energy Efficiency

Elevators and Escalators can consume between 5% and 15% of the energy of a building, depending on the type of building and its equipment provision.

An ISO working group have identified 18 factors affecting the energy consumption of Elevator equipment.

Elements affecting Elevator efficiency Mechanical system

The type of gearing used will affect consumption;

Worm gearbox’s are less efficient than helical gearbox’s. Typically 70%

Worm drive gearboxes have an efficiency significantly lower in the reverse direction compared to the forward direction, can be as low as 30%.

Generally the simpler roping systems 1:1 tend to be the more efficient.

Reducing the weight of the empty car has the advantage of also reducing the counterbalance weight and hence the energy consumption.

Drive sheave efficiency

Idler sheave efficiency

Roping (1:1, 2:1 etc)

Guidance system (Rails/Slider/Rollers)

Counterbalancing ratio

Compensation system

Drive system

Generally traction Elevators are considered to be more efficient than Hydraulic Elevators.

Hydraulic system are beginning to appear that use pressurised accumulators to recover energy

It is also considered that VVVF based drives are the most efficient compared to variable voltage, ward-leonard, DC or two speed systems.

The choice of drive system is often governed by capital cost, the operating costs are rarely considered. Free market energy pricing is beginning to affect this view.

Motor efficiency

Gear efficiency

Regen energy management

Acceleration/Deceleration profile

Creeping/Levelling time

Brake consumption

Control system

The values selected for speed, acceleration and jerk, often dictated by the traffic design and ride comfort requirements. Will affect the energy consumption.

Some control and Drive systems can optimise the energy used for the next journey dependent on the car load.

The traffic control algorithm influences how the traffic demand is handled. Under heavy demand conditions a hall call allocation system can be inherently more efficient as it groups passengers travelling to the same floors together.
Controller power consumptionDoor system (Drive, Passenger detection etc.)
Traffic/Dispatcher efficiency

Electrical system

The efficiency of various components is important;

Motor efficiency

Losses due to poor Power factor

Supply harmonic distortion

Copper losses

Car lighting and HVAC

Is energy recovered from the system and how is this stored/handled.

The Hong Kong Government has proposed limiting the size of hoist motor as a means of limiting energy consumption and has published a guide and code of practice.

Power factor

Heating and cooling

Gearless

It is generally considered that employing a permanent magnet gearless motor can offer a 30% reduction in energy consumption compared to its geared counterpart.

Operating in the reverse direction is considerably more efficient than with worm driven gearboxes.

This means more energy can be recovered from the system. Which on the down side can put more stress on any braking resistor power ratings, but can also make regenerative systems more cost effective/viable.

Common DC Bus

Regenerative drives

Simply connect two UnidriveSP’s together and configure one in Regen mode for a full 4Q solution. – No braking resistor required, Sinusoidal input current – no low order harmonics.